grid shows up on terrain renders

Eyekonography

Hi,

When I render most of the terrains in Iray, I get a gridwork showing on the render. The attached picture is from the New Colony set, just the ground terrain rendered in Iray. I get the same problem if I render the ground from the Iray SkyDome set. There must be a setting I have that is causing this, since it is not just with one terrain. Anyone have any ideas?

Medzin

Under render settings--->Environment, change "Draw Ground" to off

Eyekonography

Thanks for the suggestion, but that didn't make any difference. I even tried it with Sun and Sky only, and it still turned out the same way, with the grids.

mjc1016

What is the ground prop?

Are you using Iray materials? converting to the IrayUber shader?

Is there any displacement maps on the ground?

If so, have you set the subdivision higher?

JD_Mortal

Looks like JPG or standard low-quality image "blending" of tween-pixels. That depends on the code that tries to "fix" JPG issues. Even if it is a PNG or BMP or TIFF, it may actually be just a JPG, converted to one of those other formats. Have to check out the image in an actual image editor, and see what detail is lost. (If you see line-patterns, it is just a JPG reconverted to one other format.)

The only cure for that is a higher resolution image. It is "guessing" what the inbetween pixel colors are, and doing a bad job at it. That is a common issue with upsampled images.

JPG uses a horrible "checker-pattern" for compression. Resulting in boxes and diagonal lines and ugly squares that do not blend well. Thus, the rare use in rendering, on a professional level. It is an old horrible super-compression that eats-up details and was only good when quality was not an issue.

For massive images, it does not matter as much, since there are often more pixels to correct the issues. However, when you super-size the images, you amplify the issues.

A cheap way to subdue that zoomed-in area, is to project another image over that image. Thus, keeping the distant area the way it is, while adding the required detail to the area near the camera itself.

NOTE: PNG's that were once JPG's natively, are just as horrible, as they just capture the JPG errors and lock them into a BMP (bit-mapped) image. Most photographs that are from a digital camera will have that issue, as they commonly save in JPG or some other horrible compression format, unless the camera is setup to save photographs as RAW, or TIFF. (Then you still have CMOS interpolation issues, which shows as grids too.)

The image below is what "softened JPEG" compression looks like... Actually, before interpolation, it looks like checkerboards and diagonal lines, forming ugly squares.

This is what JPG looks like as actual "pixels", when it alters the image... (You see the grids) that you seem to see on your rendering, unsoftened. They show-up more in higher contrast areas, which is why JPG is the worst compression for anything that has high contrast areas. Unless there is TONS of high contrast, like stones and gravel.)

Since your grids change with the perspective, that implies it is "in the image", not an issue with rendering.

Paint "Noise" over those areas, after rendering, to hide the grids. Noise is +/- one R or G or B value, to disrupt patterns, like you would often find in the ground and in nature. (Clone-paint for more detailed control. Adjusting the blend-mode of the layer.)

Hue to target, shade to target, and color to target, are also good post-work tools, for fixing those issues. (When you can't get a new larger image for rendering.)